What is Lymphoma?

To understand lymphoma, and perhaps any type of cancer, it is useful to first understand a couple of ‘human-body basics’. It is estimated that the human body is made of over 50 trillion cells (50,000,000,000,000). It is also estimated that every hour, the human body has to replace over 1 billion cells (yes, 1,000,000,000!). Every one of these 50 trillion cells are organized into one of 4 tissues, which include epithelial tissue, connective tissue, muscle and nervous tissue.

Epithelial tissue lines various organs and plays a role in protecting the body from the outside environment, secreting proteins necessary to fend off infection, and in absorbing nutrients. The overwhelming number of cancers are derived from epithelial tissues (breast, prostate, lung, colon, ovarian, bladder, for example). Connective tissue includes bone and ligaments, as well as all the cells that make up the blood, or hematopoietic system. Muscle tissue makes up muscle, and nervous tissue makes up the brain, spinal cord, and peripheral nerves.

What is important to keep in mind, is that these 4 tissues are assembled in various ways to make up the 78 different organs that together make up the human body. These 78 different organs are then configured into systems or networks, which define the 13 different organ systems that make up the human body. So, when someone says cancer to an oncologist, the doctor is thinking: (1) which organ (lung, breast, prostate, blood, colon, etc.), and (2) what cell (epithelial, hematopoietic, mesenchymal, nervous, etc.).

While it is widely touted that there are over 200 different kinds of cancer, this number does not reflect all the different sub-types of a specific cancer. Thus, among these 200 types of cancer, which includes the two diseases of our interest, non-Hodgkin lymphoma and Hodgkin lymphoma, it does not include the now recognized 68 different kinds of NHL, nor the 4 different kinds of Hodgkin lymphoma. Thus, when someone says I have cancer, it is usually not very helpful to the oncologist (that is, the cancer doctor), because it lacks the detail defining the organ and cell of origin. Each cancer is often associated with its own unique behavior, prognosis and treatment.

Similarly, the term lymphoma today is also only marginally useful to the cancer doctor, because each of the 68 or so different kinds of lymphoma have their own unique behavior, prognosis, and management. Lymphoma refers only to a cancer of a specific type of white blood cell called the lymphocyte. Lymphocytes (or lymphoid blood cells) are different from myeloid blood cells, which include neutrophils, eosinophils and basophils, which when they become cancerous or malignant, are typically referred to as leukemia. Lymphocytes play a very important role in the immune system, especially in fighting viruses and in controlling and mediating innumerable immunological reactions in the body.

Lymphocytes too come in 3 basic types, including B-lymphocytes, T-lymphocytes and NK cells, all of whom are born in the bone marrow. After leaving the bone marrow, they traverse the body, where they enter lymph nodes. This stop in the lymph nodes (or thymus for T-cell) is in essence an education on how and what role that cell will play in your body’s immune defense.

One way to think about the diversity of lymphomas is to think about the steps in life a person takes: from birth to adolescence, teenager to young adult, retired adult to senior citizen, the natural development of a lymphocyte through the stages of maturation, like a person over time, creates the diversity of lymphomas. Knowing precisely which one you have dictates everything your oncologist needs to know about how best to approach that specific disease.